Nitrogen Dioxide (NO2)

Nitrogen Dioxide (NO₂) is a secondary pollutant, produced by combustion in the presence of air.  At very high temperatures and pressures such as those found in power stations, car engines etc. chemical reactions occur which bond the oxygen and nitrogen that are naturally found in the atmosphere to form Nitrous Oxide (NO).

NO is almost immediately oxidised into NO₂ on contact with atmospheric oxygen. NO₂ is formed by very few natural processes, this is due to the inert nature of Nitrogen.  Nitrogen normally occurs as dinitrogen (N2) and the two nitrogen atoms are joined by a double strength bond. 

The main probelm with NO₂ is that it is an irritant, so it can effect human health.  It does this by inflamming the bronchial tract and generally aggravating the repsiratory system to the point that people become more susceptable to diseases like bronchitus, asthma, allergies etc. To learn more go to Lung Foundation Air Quality Page

Also, NO₂ contributes to the production of photochemical smog which can be more toxic to human health.  Further it will eventually breakdown to produce nitric acid and hence give rise to acid rain which harms the environment. 

In Shrewsbury there is a particular problem with NO₂ pollution at several 'pinchpoints' around the town, where vehicular trafic becomes congested.  These areas have been designated as Air Quality Management Areas because they breach government objectives for NO₂.

A detailed review and assessment of levels of NO2 has been conducted by the Borough Councils Environmental Health team.  The main findings are that: -

• The main source of NO₂ is vehicular traffic
• The 3 AQMA's are still exceeding government objectives for NO₂
• Levels of NO2 are likely to get worse if action to tackle traffic congestion is not taken
• The town centre area has seen increased levels of NO₂, to the extent that a new AQMA (03A) was declared in February 2006.

The full findings of the NO₂ assessment can be downloaded by clicking on the icon below.  Be aware that this is a large PDF file, which requires Adobe Acrobat software to view, and may take some time to fully download for those without broadband.

(pdf format, 3.5mb)

A Further Assessment for NO₂, including source apportionment to quantify the effectiveness of measures within AQMA 03A was completed in May 2006. This can be downloaded by clicking on the icon below.  Be aware that this is a large PDF file, which requires Adobe Acrobat software to view, and may take some time to fully download for those without broadband.

(pdf format, 1.3mb)